1. Technical Field
The present invention relates to a base material with a single-crystal silicon carbide film having a single-crystal silicon carbide film which is a wide bandgap semiconductor material formed on a silicon substrate or on a single-crystal silicon film formed on a substrate, a method of producing a single-crystal silicon carbide film, and a method of producing a base material with a single-crystal silicon carbide film, and, particularly to a base material with a single-crystal silicon carbide film having a cubic silicon carbide thin film formed on a silicon substrate, a method of producing a single-crystal silicon carbide film in which a cubic silicon carbide thin film is formed on a silicon substrate, and a method of producing a base material with a single-crystal silicon carbide film.
2. Related Art
Due to having large aperture, high quality, and a low price, single-crystal silicon has been used as a substrate for growing the single crystals of many materials.
Among the materials, cubic silicon carbide (3C-SiC) which is a wide bandgap semiconductor material with a wide bandgap of 2.2 eV (300 K) is expected to be a semiconductor material for next generation low-loss power devices and, particularly, is considered extremely useful from the standpoint of the possibility of single crystal growth (heteroepitaxy) on a low-cost silicon substrate.
Incidentally, since the lattice constant of cubic silicon carbide is 4.359 angstroms and is thus about 20% smaller than the lattice constant of cubic silicon (5.4307 angstroms), it is likely that many voids or misfit dislocations will occur in epitaxially grown cubic silicon carbide, and thus it is difficult to grow high-grade cubic silicon carbide.
Therefore, as a method of alleviating the difference in the lattice constant (lattice mismatch) between a silicon substrate and cubic silicon carbide, a method using a Silicon On Insulator (SOI) structure is suggested (JP-A-2003-224248).
In this method, an SOI substrate having a buried insulator (I layer) composed of a surface silicon layer (Si layer) with a predetermined thickness and silicon oxide is placed in a heating furnace, and the atmospheric temperature in the heating furnace is elevated while a mixed gas of hydrogen gas and a hydrocarbon-based gas is supplied to the heating furnace, thereby modifying the surface silicon layer on the SOI substrate to a single-crystal silicon carbide film. In this method, since all of the thin surface silicon layer is carbonized, and thus the produced single-crystal silicon carbide film is physically separated from the single-crystal silicon substrate and comes into contact with the buried insulator (I layer) that is liable to soften, it is possible to alleviate lattice mismatch-induced stress and also to form a single-crystal silicon carbide film for which crystal defects are suppressed.
However, in the above method using the SOI structure in the related art, it is necessary to make the film thickness as thin as about 10 nm or less in order to carbonize all of the surface silicon layer, but it is difficult to form a surface silicon layer having such a film thickness on the buried insulating layer, and thus there is a problem in that it is not easy to manufacture a substrate having such an SOI structure that is excellent in terms of uniformity.
In addition, the single-crystal silicon carbide film is not in contact with the single-crystal silicon substrate, but is still in contact with the buried insulating layer made of silicon oxide, and therefore there are problems in that silicon oxide has difficulty in sufficiently softening in the vicinity of 1100° C. which is the temperature at which the single-crystal silicon carbide film grows, and it is not possible to sufficiently develop the effect of stress alleviation.
As such, there has been demand for a single-crystal silicon carbide film and a method of producing a single-crystal silicon carbide film, in which the influence of stress induced by lattice mismatch on the single-crystal silicon carbide film is reduced in order to grow a sufficiently high-grade single-crystal silicon carbide film during epitaxy.